Nagai et al. BMC Public Health (2017) 17:340
DOI 10.1186/s12889-017-4247-2
RESEARCH ARTICLE
Open Access
Lifestyle-related factors that explain
disaster-induced changes in socioeconomic
status and poor subjective health: a crosssectional study from the Fukushima health
management survey
Masato Nagai1,2* , Tetsuya Ohira1,2, Wen Zhang2, Hironori Nakano1,2, Masaharu Maeda1,3, Seiji Yasumura4,
Masafumi Abe1 and Fukushima Health Management Survey
Abstract
Background: Socioeconomic status (SES) and lifestyle-related factors are determinants of subjective health.
However, changes in SES are inevitable in times of natural disaster, while lifestyle-related factors remain modifiable.
The aim of this study was to use a cross-sectional approach to examine lifestyle-related factors that may attenuate
the negative impact of disaster-induced changes in SES on poor subjective health.
Methods: We analyzed 33,350 men and women aged 20–64 years who were living in evacuation zones due to the
radiation accident in Fukushima, Japan. Disaster-induced changes in SES were defined by living arrangements and
working conditions. Using Poisson regression analysis adjusted for confounders (model 1) and lifestyle-related
factors as intermediate variables (model 2), we compared the prevalence ratios (PRs) of poor subjective health of
participants who did not undergo disaster-induced changes in SES (did not become unemployed, income did not
decrease, and living in relative’s home/own home) with that of participants who did undergo disaster-induced
changes in SES (became unemployed, decreased income, or lived in an evacuation shelter, temporary housing, or
rental housing/apartment). We calculated the percentage of excess risks explained by lifestyle-related factors as
follows: ((PRmodel 1 − PRmodel 2)/(PRmodel 1–1)) × 100.
Results: Disaster-induced changes in SES were significantly associated with poor subjective health. The PRs (95%
CIs) among participants who underwent disaster-induced changes in SES were 2.02 (1.81–2.24) for men and 1.80 (1.
65–1.97) for women. After adjusting for lifestyle-related factors, we found that the PRs in men and women were
remarkably attenuated, decreasing to 1.56 (1.40–1.73) and 1.43 (1.31–1.55), respectively. Controlling for lifestylerelated factors resulted in PR attenuation by 45.1% (men) and 46.3% (women). Satisfaction of sleep and
participation in recreation and community activity particularly contributed to this attenuation.
Conclusions: While disaster-induced changes in SES are unavoidable, lifestyle-related factors have the potential to
attenuate the impact of these changes on poor subjective health.
Keywords: Socioeconomic status, Subjective health, Disaster, Lifestyle
* Correspondence: [email protected]
1
Radiation Medical Science Center for the Fukushima Health Management
Survey, Fukushima Medical University, Fukushima, Japan
2
Department of Epidemiology, Fukushima Medical University School of
Medicine, Fukushima, Japan
Full list of author information is available at the end of the article
© The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Nagai et al. BMC Public Health (2017) 17:340
Background
On March 11, 2011, the Great East Japan Earthquake
struck off the Pacific coast of northern Japan. The earthquake generated a tsunami, which caused a radiation accident at the Fukushima Daiichi Nuclear Power Plant
and led to the evacuation of over 160,000 residents of
Fukushima Prefecture. Many of the victims permanently
lost their homes and were forced to live in temporary
housing or shelters.
Subjective health is a recognized comprehensive index
of public health for evaluating the health of a population.
It has been validated as a marker for predicting various
health outcomes, such as diabetes [1], myocardial infarction [2], and mortality [3], independent of other health
determinants. Socioeconomic status (SES), which comprises variables such as working conditions, income, and
education, is associated with subjective health [4–11],
namely, low SES consistently results in poor subjective
health. In addition to SES, lifestyle-related factors, such
as smoking [7, 12], alcohol consumption [13], physical
activity [7, 12, 13], and sleeping [14, 15], are determinant
factors of subjective health. These factors are also associated with SES [16–20]. Thus, it is hypothesized that
changes that lower SES induce poor subjective health
through lifestyle changes.
Importantly, disasters have a substantial impact on lifestyles and SES; specifically, disaster-induced change in
SES and subsequent lower subjective health are unavoidable following a disaster. However, lifestyle-related factors
are still modifiable. Thus, there are opportunities to modify lifestyle factors through various recovery support efforts for disaster victims. The association between SES
and subjective health has been well researched [4–11];
however, the extent to which lifestyle-related factors explain the impact of disaster-induced changes in SES on
subjective health has not been examined.
The purpose of this study was to explain the mediating
effects of lifestyle-related factors on the association between disaster-induced change in SES and subjective
health. We conducted a cross-sectional study of 33,350
Japanese adults who lived in the evacuation zone resulting from the nuclear accident in Fukushima in 2011.
This study examined: 1) the impact of disaster-induced
changes in SES on poor subjective health and 2) the mediating effects of lifestyle-related factors on that impact.
Page 2 of 9
7–15 years, and ≥16 years) was delivered in January 2012
to all residents who lived in the evacuation zones caused
by the radiation accident on March 11, 2011, in Fukushima Prefecture. The evacuation zone was a governmentdesignated area (20 km radius) around the nuclear power
plant. Of the target population of 180,604 participants
aged ≥16 years, 73,433 (40.7%) responded.
We excluded the following participants from this
study: those who did not provide information about subjective health (n = 1879) or current living arrangements
(n = 14,859), those who reported “other” for current
living arrangements (n = 2761), and those aged <20 or
≥65 years (n = 20,584). We excluded the latter set of
participants because this group included many participants who were not working due to their status as students or retirees. Thus, we analyzed a total of 33,350
participants (14,913 men and 18,437 women).
The study protocol was approved by the Ethics Committee of Fukushima Medical University. Participants who
returned the self-administered questionnaires were considered to have consented to participate.
Socioeconomic status
The self-administered questionnaire included questions
about disaster-induced changes in SES that assessed participants’ living and working situations. Change in living
arrangements was assessed through each participant’s response to the question: “How have your living arrangements changes?” The participants indicated their current
residence by circling one of the following: “evacuation shelter”, “temporary housing”, “rental housing/apartment”, “relative’s home”, or “own home”. We defined participants as
having a “change in living arrangements” if their response
was “evacuation shelter”, “temporary housing”, or “rental
housing/apartment”. Change in working conditions was
assessed with the question: “Has your work situation changed as a result of the natural disaster or nuclear accident?”.
If participants responded “yes”, they checked the following
items as appropriate: “became unemployed” or “income has
decreased”. We defined participants as having a disasterinduced change in SES if they provided any of the above responses (i.e., “evacuation shelter”, “temporary housing”,
“rental housing/apartment”, “became unemployed”, or “income has decreased”).
Methods
Subjective health
Study participants
The self-administered questionnaire included a question on subjective health. Subjective health was assessed
through each participant’s response to the question: “Describe your current state of health”. The participants chose
one of the following answers: very good (men 5.6%; women
3.9%), good (men 18.3%; women 13.8%), normal (men
61.3%; women 66.5%), poor (men 13.4%; women 14.4%), or
The data for this study were derived from the Mental
Health and Lifestyle Survey, which is included in the
Fukushima Health Management Survey, a detailed description of which can be found elsewhere [21]. Briefly, a
self-administered questionnaire on mental health and various lifestyle habits according to age category (0–6 years,
Nagai et al. BMC Public Health (2017) 17:340
very poor (men 1.4%; women 1.4%). “Poor subjective
health” was defined by the answers “poor” or “very poor”.
Lifestyle-related factors
We regarded smoking, alcohol consumption, sleep,
participation in recreation and community activities,
and exercise as lifestyle-related factors. These factors
were assessed using the following questions and associated choices: “Do you smoke cigarettes (excluding
cigars and pipes)?” (“never smoke”, “quit”, or “current
smoker”); “Do you drink alcohol?” (“don’t drink or
only rarely (less than once/month)”, “quit”, or “drink
(at least once a month)”); “Are you satisfied with the
quality of your sleep over the past month (regardless
of sleep duration)?” (“satisfied”, “slightly dissatisfied”,
“quite dissatisfied”, or “very dissatisfied or haven’t
slept at all”); “Do you participate in recreation (karaoke or gateball, etc.) and community activities (festivals, etc.)?” (“never or rarely”, “sometimes”, or
“often”); and “Do you exercise regularly?” (“almost
every day”, “2–4 times/week”, “once/week”, or “almost
never”).
Statistical analysis
We used Poisson regression with robust error variance to
derive prevalence ratios (PRs) and 95% confidence intervals
(CIs) of poor subjective health according to disasterinduced changes in SES and to adjust for potential confounding factors because the prevalence of poor subjective
health was not rare (≥10%) [22]. We calculated using the
SAS software package, version 9.3 (Cary, NC, USA). Participants who did not undergo disaster-induced changes in
SES (i.e., “living in relative’s home” or “own home” and did
not “become unemployed” and “decrease income”) were selected as the reference group. All P values were two-tailed,
and differences at P < 0.05 were accepted as statistically significant. In model 1, we considered the following variables
to be potential confounding factors: age (5-year categories:
20–24, 25–29…up to and including 60–64 years), history of
disease (yes or no: hypertension, diabetes, hyperlipidemia,
stroke, heart disease, cancer, chronic hepatitis, pneumonia,
bone fracture, or thyroid disease), history of mental illness
(yes or no), activities of daily living (go shopping for daily
necessities: can do by myself or can’t do by myself), education (elementary school junior high school, high school,
or vocational college/ junior college or university
(4 years) graduate school), and evacuation place (Fukushima or other prefectures). In model 2, we further adjusted
for the following lifestyle-related factors: smoking (never
smoked, quit, or current smoker), alcohol consumption
(less than once/month, quit, or at least once a month), satisfaction of sleep (satisfied, slightly dissatisfied, or complaint
(quite dissatisfied, or very dissatisfied or haven’t slept at all),
participation in recreation and community activity (never
Page 3 of 9
or rarely, sometimes, or often), and regular exercise (almost
every day, 2–4 times/week, or ≤1 time/week). Additionally,
we repeated the analyses for each disaster-induced change
in SES (i.e., change in living arrangements, became unemployed, and decrease income).
We calculated the percentage of excess risks explained by
lifestyle-related factors as follows: (PRmodel 1 − PRmodel 2)/
(PRmodel 1–1)) × 100 [23].
Results
Characteristics by disaster-induced change in SES
The characteristics of the study participants according to
disaster-induced change in SES for men and women are
shown in Table 1. For both sexes, the prevalence of poor
subjective health among participants with a disasterinduced change in SES showed an almost two-fold increase.
Compared with participants who did not undergo disasterinduced changes in SES, participants who did undergo
disaster-induced changes in SES scored lower with respect
to the following factors: mean age, prevalence of evacuation
to Fukushima prefecture, never smoked, satisfied sleep,
often participation in recreation and community activity,
disease history in women, alcohol consumption less than
once a month for women, and inability at go shopping for
daily necessities by myself for men.
Disaster-induced change in SES and poor subjective
health
Table 2 shows the PRs of poor subjective health due to
disaster-induced changes in SES with 95% CIs. The association between disaster-induced changes in SES and poor
subjective health was attenuated after adjustment for
lifestyle-related factors. In model 2, the PRs (95% CIs)
among participants who underwent disaster-induced
changes in SES decreased from 2.02 (1.81–2.24) in men
and 1.80 (1.65–1.97) in women to 1.56 (1.40–1.73) in men
and 1.43 (1.31–1.55) in women (model 1). The percentage
of excess risk explained was 45.1% for men and 46.3% for
women.
Additional file 1: Tables S1 and S2 show the PRs of
poor subjective health according to each disasterinduced change in SES with 95% CIs. We also observed
an attenuation in the impact of change in living arrangements, became unemployed, and decreased income on
poor subjective health after adjusting for lifestyle-related
factors in both sexes.
Lifestyle-related factors associated with disaster-induced
changes in SES and poor subjective health
To examine which items enhanced the association between disaster-induced changes in SES and poor subjective health, Table 3 shows the PRs with 95% CIs for
model 1 plus each lifestyle-related factor. The impact of
disaster-induced changes in SES on subjective health
Nagai et al. BMC Public Health (2017) 17:340
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Table 1 Characteristics by disaster-induced changes in socioeconomic status among 14,913 men and 18,437 women aged 20–
64 years in Fukushima Health Management Survey, Fukushima, 2012
Men
Women
Unchanged
Changed
No. of participants
4133
10,780
Mean age (years) (SDa)
49.1 (12.6)
46.7 (12.8)
b
P value
<0.001
Unchanged
Changed
5302
13,135
48.0 (12.6)
45.1 (12.8)
P value
<0.001
Prevalence of poor subjective health (%)
8.6
17.2
<0.001
10.0
18.1
<0.001
History of disease (%)
53.6
54.2
0.520
44.7
41.2
<0.0001
Hypertension
32.2
32.8
0.483
23.9
22.0
0.005
Diabetes
15.8
15.8
0.979
9.7
8.9
0.113
Dyslipidemia
30.7
33.1
0.005
25.9
23.8
0.003
Cancer
2.3
2.4
0.865
3.6
2.7
0.001
Stroke
2.4
2.5
0.684
1.2
1.3
0.882
Cardiac disease
5.3
5.7
0.306
3.1
3.2
0.724
Liver disease
1.8
2.2
0.108
1.3
1.1
0.206
Pneumonia
2.0
2.1
0.502
2.0
2.1
0.679
Fracture
3.7
3.2
0.160
4.3
3.5
0.009
Thyroid disease
1.2
0.8
0.032
4.7
4.4
0.412
4.8
4.5
0.405
4.2
5.7
<0.0001
1.7
1.2
0.008
1.2
1.0
0.202
28.2
28.2
0.053
34.2
34.7
<0.0001
History of mental illness (%)
Activities of daily living
(Go shopping for daily necessities) (%)
Can’t do by myself
Educational status (%)
Vocational college/ junior college,
university•graduate school
High school
54.5
56.1
51.3
54.4
Elementary school •junior high school
17.3
15.7
14.5
11.0
Fukushima prefecture
96.3
77.2
95.7
72.7
Other prefectures
3.7
22.8
4.3
27.4
Evacuation place (%)
<0.001
<0.001
Smoking (%)
Never smoked
26.2
22.3
81.0
71.1
Quit
33.8
31.5
<0.001
8.9
12.2
Current smoker
39.9
46.2
10.1
16.8
Less than once/month
27.9
26.3
66.1
60.9
Quit
2.8
2.5
1.6
2.4
At least once a month
69.3
71.3
32.3
36.7
Satisfied
45.9
31.7
34.5
24.2
Slightly dissatisfied
44.0
47.7
52.4
51.9
Complaint
10.2
20.6
13.1
23.9
Never or rarely
50.9
70.9
59.5
75.6
Sometimes
35.9
23.6
33.7
20.7
<0.001
Alcohol consumption (%)
0.051
<0.001
Satisfaction of sleep (%)
<0.001
<0.001
Participatin in recreation and
community activity (%)
<0.001
<0.001
Nagai et al. BMC Public Health (2017) 17:340
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Table 1 Characteristics by disaster-induced changes in socioeconomic status among 14,913 men and 18,437 women aged 20–
64 years in Fukushima Health Management Survey, Fukushima, 2012 (Continued)
Often
13.2
5.5
6.8
3.7
Almost every day
11.5
10.8
7.7
7.7
2–4 times /week
14.4
≤1 time /week
74.1
13.7
14.5
14.3
75.6
77.8
78.1
Regular exercise (%)
0.190
0.880
SD standard deviation
b
P values were calculated by chi-square test (categorical variables), or t-test (continuous variables)
a
was attenuated after adjusting for satisfaction of sleep or
participation in recreation and community activity. The
PRs (95% CIs) decreased to 1.64 (1.48–1.82) and 1.84
(1.66–2.05) in men, respectively, and to 1.47 (1.35–1.61)
and 1.71 (1.56–1.87) in women, respectively. The corresponding percentage of excess risk explained was 37.3
and 17.6% in men, respectively, and 41.3 and 11.3% in
women, respectively. However, the adjustment for other
lifestyle-related factors (smoking, alcohol consumption,
and regular exercise) did not change the PRs of the association between disaster-induced changes in SES and
poor subjective health.
Table 4 shows the impact of each lifestyle-related factor on poor subjective health. Satisfaction of sleep and
participation in recreation and community activity was
significantly associated with poor subjective health.
Compared with participants who were satisfied with
their sleep, participants who were slightly dissatisfied
had PRs of 2.94 (men, 2.51–3.44) and 2.67 (women,
2.28–3.12), and those who had complaints had PRs of
8.26 (men, 7.08–9.63) and 7.63 (women, 6.55–8.89).
Compared with participants who often participated in
recreation and community activity, participants who
sometimes participated had PRs of 1.12 (men, 0.90–
1.40) and 1.28 (women, 1.01–1.63), and those who never
or rarely participated had PRs of 1.65 (men, 1.34–2.03)
and 1.75 (women, 1.39–2.20).
While we adjusted for the effect of age, it is possible
that disaster-induced changes in SES differed substantially between age groups. After stratifying by age (<40
and ≥40 years), we observed comparable results to those
above (data not shown). Lifestyle-related factors that
mediated the association between disaster-induced
changes in SES and poor subjective health did not differ
between age groups.
The above tendency was also observed with respect to
the association between changed living arrangements
(relative’s home/own home, rental housing/apartment,
or evacuation shelter/temporary housing), became unemployed, decreased income, and poor subjective health
(Additional file 1: Tables S1, S2, and S3). However, participation in recreation and community activity did not
attenuate the impact of evacuation shelter/temporary
housing and became unemployed on poor subjective
health for women and did not attenuate the impact of
decreased income for men and women.
Discussion
Disaster-induced changes in SES (changed living arrangements, became unemployed, and decreased
Table 2 Prevalence ratios and 95% confidence intervals of poor subjective health by disaster-induced changes in socioeconomic
status among 14,913 men and 18,437 women aged 20–64 years in Fukushima Health Management Survey, Fukushima, 2012
Men
Women
Unchanged
Changed
Unchanged
Changed
No. of participants
4133
10,780
5302
13,135
No. of cases
354
1858
529
2383
Crude
1.00 (reference)
2.01 (1.81–2.24)
1.00 (reference)
1.82 (1.66–1.99)
Age-adjusted
1.00 (reference)
2.10 (1.88–2.34)
1.00 (reference)
1.93 (1.77–2.11)
Model 1a
1.00 (reference)
2.02 (1.81–2.24)
1.00 (reference)
1.80 (1.65–1.97)
Model 2b
1.00 (reference)
1.56 (1.40–1.73)
1.00 (reference)
1.43 (1.31–1.55)
Percentage excess risks explained
45.1%
a
46.3%
Model 1 was adjusted for age (5-year categories), history of diseases (hypertension, diabetes, hyperlipidemia, cancer, stroke, heart disease, chronic hepatitis,
pneumoia, bone fracture, or thyroid disease), history of mental illness (yes or no), activities of daily living (go shopping for daily necessities; can do by myself or
can’t do by myself), education (elementary school • junior high school, high school, or vocational college/ junior college or university • graduate school), and
evacuation place (Fukushima or other prefecture)
b
Model 2 was further adjusted Model 1 for smoking (never smoked, quit, or current smoker), alcohol consumption (less than once a month, quit, or at least once
a month), satisfaction of sleep (satisfied, slightly dissatisfied, or complaint), participation in recreation and community activity (never or rarely, sometimes, or
often), and regular exercise (almost every day, 2–4 times/week, or ≤1 time /week)
Nagai et al. BMC Public Health (2017) 17:340
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Table 3 Prevalence ratios and 95% confidence intervals of poor subjective health by disaster-induced changes in socioeconomic status after adjusted for each lifestyle-related factors among 14,913 men and 18,437 women aged 20–64 years in Fukushima Health
Management Survey, Fukushima, 2012
Unchanged
Changed
4133
10,780
Percentage of
excess risk explained
Men
No. of participants
No. of cases
354
1858
Model 1a
1.00 (reference)
2.02 (1.81–2.24)
−
+ Smoking
1.00 (reference)
2.01 (1.81–2.24)
1.0%
+ Alcohol consumption
1.00 (reference)
2.02 (1.82–2.25)
0.0%
+ Satisfaction of sleep
1.00 (reference)
1.64 (1.48–1.82)
37.3%
+ Participation in recreation and community activity
1.00 (reference)
1.84 (1.66–2.05)
17.6%
+ Regular exercise
1.00 (reference)
2.02 (1.81–2.24)
0.0%
No. of participants
5302
13,135
No. of cases
529
2383
Women
1.00 (reference)
1.80 (1.65–1.97)
−
+ Smoking
1.00 (reference)
1.77 (1.64–1.96)
3.8%
+ Alcohol consumption
1.00 (reference)
1.79 (1.64–1.96)
1.3%
+ Satisfaction of sleep
1.00 (reference)
1.47 (1.35–1.61)
41.3%
Model 1
+ Participation in recreation and community activity
1.00 (reference)
1.71 (1.56–1.87)
11.3%
+ Regular exercise
1.00 (reference)
1.81 (1.66–1.97)
−1.3%
a
Model 1 was adjusted for age (5-year categories), history of diseases (hypertension, diabetes, hyperlipidemia, cancer, stroke, heart disease, chronic hepatitis,
pneumoia, bone fracture, or thyroid disease), history of mental illness (yes or no), activities of daily living (go shopping for daily necessities; can do by myself or
can’t do by mysefl), education (elementary school • junior high school, high school, or vocational college/ junior college or university • graduate school), and
evacuation place (Fukushima or other prefecture)
income) resulting from a natural disaster are associated
with poor subjective health and are unavoidable. The
present study yielded the following results: (1) The percentage of excess risk explained by lifestyle-related factors was 45.1% in men and 46.3% in women; and (2)
The lifestyle-related factors of satisfaction of sleep and
participation in recreation and community activity contributed to the attenuated association between disasterinduced changes in SES and poor subjective health.
Previous studies identified a significant association
between unemployment and poor subjective health [4, 7,
9, 11]. As in previous studies, we found that became unemployed was significantly associated with poor subjective health. We also showed that decreased income and
change in living arrangements were significantly associated with poor subjective health; for women, this association existed even in the absence of a decreased income.
These results are in accordance with those of previous
studies [10, 24]. Kennedy et al. showed that the odds ratios (ORs) of fair or poor subjective health increased
with a decrease in annual income [10]. Sugimoto et al.
found that the prospect that “income will decrease” nonsignificantly increased the risk of poor subjective health
(OR, 1.31; 95% CI, 0.95–1.84) among youth, which
included evacuees from the Great East Japan Earthquake
[24]. Those authors also showed that an evacuation
period of over 4 weeks significantly increased the risk of
poor subjective health (OR, 1.44; 95% CI, 1.06–1.97).
After we adjusted for lifestyle-related factors, we found
that the above associations were still statistically significant; however, the PRs were remarkably attenuated. We
examined which lifestyle-related factors attenuated the
association between disaster-induced changes in SES
and subjective health. In both sexes, we found that the
PRs decreased remarkably after adjustments for satisfaction of sleep and participation in recreation and community activity. Silva-Costa et al. showed that insufficient
sleep significantly increased the risk of poor subjective
health in nurses [14]. Geiger et al. showed that the ORs
of poor subjective health increased with an increase in the
number of days of insufficient rest/sleep [25]. Sleep problems cause various negative health outcomes, such as increased blood pressure and heart rate [26], mental health
problems [27], and worse health-related quality of life
[28]. In contrast, social participation has been associated
with a decrease in functional disability [29] and depressive
symptoms [30] and an improvement in subjective health [7,
31]. Changes in SES have reportedly caused dissatisfaction
Nagai et al. BMC Public Health (2017) 17:340
Page 7 of 9
Table 4 Prevalence ratios and 95% confidence intervals of poor
subjective health by lifestyle-related factors among 14,913 men
and 18,437 women aged 20–64 years in Fukushima Health Management Survey, Fukushima, 2012
Model2
Men
Women
Never smoked
1.00 (reference)
1.00 (reference)
Quit
1.04 (0.94–1.15)
1.07 (0.97–1.19)
Current smoker
1.01 (0.92–1.12)
1.08 (0.99–1.17)
Less than once a month
1.00 (reference)
1.00 (reference)
Quit
1.32 (1.13–1.56)
1.09 (0.92–1.29)
At least once a month
0.87 (0.81–0.94)
1.03 (0.96–1.10)
Satisfied
1.00 (reference)
1.00 (reference)
Slightly dissatisfied
2.94 (2.51–3.44)
2.67 (2.28–3.12)
Complaint
8.26 (7.08–9.63)
7.63 (6.55–8.89)
Smoking
Alcohol consumption
Satisfaction of sleep
Participatin in recreation and community activity
Often
1.00 (reference)
1.00 (reference)
Sometimes
1.12 (0.90–1.40)
1.28 (1.01–1.63)
Never or rarely
1.65 (1.34–2.03)
1.75 (1.39–2.20)
Almost every day
1.00 (reference)
1.00 (reference)
2–4 times /week
0.94 (0.81–1.09)
0.93 (0.81–1.07)
≤1 time /week
1.04 (0.92–1.18)
1.05 (0.93–1.18)
Regular exercise
a
Model 2 was adjusted for age (5-year categories), history of diseases
(hypertension, diabetes, hyperlipidemia, cancer, stroke, heart disease, chronic
hepatitis, pneumoia, bone fracture, or thyroid disease), history of mental illness
(yes or no), activities of daily living (go shopping for daily necessities; can do
by myself or can’t do by myself), education (elementary school • junior high
school, high school, or vocational college/ junior college or university •
graduate school), evacuation place (Fukushima or other prefecture), smoking
(never smoked, quit, or current smoker), alcohol consumption (less than once
a month, quit, or at least once a month), satisfaction of sleep (satisfied, slightly
dissatisfied, or complaint), participation in recreation and community activity
(never or rarely, sometimes, or often), regular exercise (almost every day, 2–4
times/week, or ≤1 time /week), and disaster-induced changes in SES
(unchanged or changed)
of sleep and failure to participation recreation and community activity [18, 32, 33]; those participants had lower subjective health because of their perceived worsened health
condition. However, the causal relationships in the above
associations are not fully understood. Thus, poor subjective
health may lead to impaired quality of sleep and nonparticipation in recreation and community activity.
Interestingly, smoking, alcohol consumption, and regular exercise were not associated with poor subjective
health in the present study. While smoking, alcohol consumption, and regular exercise are commonly recognized
as determinants of subjective health [7, 11–13, 34–36],
other studies have reported that smoking, alcohol consumption, regular exercise, and body mass index did not
explain the impact of the log of income on subjective
health [11]. Furthermore, the ORs of poor subjective
health according to employment status did not change before and after adjusting for regular exercise, body mass
index, and smoking [7]. The reason why smoking, alcohol
consumption, and regular exercise did not mediate the
impact of disaster-induced changes in SES on poor subjective health is unclear. In the present study, victims were
forced to change their lifestyles as a result of the disaster;
they had to become accustomed to life as evacuees and
had to move repeatedly. It is possible, however, that the
above lifestyle factors may not be associated with subjective health in abnormal situations such as natural disasters.
A major strength of the present study is that to the
best of our knowledge, it is the first study to clarify the
lifestyle-related factors that attenuate the impact of
disaster-induced change in SES on poor subjective
health. However, several limitations deserve consideration. First, the present study design was cross-sectional.
We did not have any information on SES, lifestyles, or
subjective health of the participants before the disaster.
Thus, we could not confirm the causality between explanatory factors and subjective health. Lifestyle modification as an intervention does not necessarily prevent
poor subjective health due to disaster-induced changes
in SES. However, in the present study, the reason for the
disaster-induced changes in SES was a natural disaster,
followed by widespread evacuations. We argue that
negative changes in lifestyle and subjective health occurred after the experience of disaster-induced changes
in SES. Second, the response rate was only 40.7%. Additionally, we excluded 23.1% of the respondents aged
20–64 years. The results of this study may thus be
affected by response and selection bias. However, the
difference in the prevalence of poor subjective health between participants with and without this exclusion was
only 0.7% point for men and 1.3% point for women.
Therefore, we consider the effect of selection bias to be
small. Importantly, we could not evaluate the response
bias because there was no basic data on disaster-induced
changes in SES, lifestyle habits, and subjective health for
non-respondents. We acknowledge both of the following
possibilities: participants with poor subjective health
tend not to respond because they are feeling down or
unwell, and/or participants with good subjective health
tend not to respond because they do not have any problems. These possibilities may have led to an overestimate
or underestimate of the impact of lifestyle-related factors
on the associations between disaster-induced changes in
SES and poor subjective health. Third, information on
disaster-induced changes in SES and lifestyle-related factors was obtained from self-reported questionnaires.
However, subjective health is an index that assesses
subjective and self-reported. Thus, not objectively
Nagai et al. BMC Public Health (2017) 17:340
measured. For example, if people who have good sleep,
as measured objectively, are dissatisfied with their own
sleep, they will likely report a poor in their own subjective health. Thus, even though exposure and mediators
are self-reported, modifying self-reported conditions will
arguably be more important and useful than focusing on
objectively measured conditions. Finally, we limited
study participants to those aged 20–64 years because
working conditions were used as part of the definition of
disaster-induced changes in SES. Therefore, the present
findings may not apply to teenagers and the elderly, and
wider generalizations must be made cautiously.
Conclusions
Our findings suggest that while SES changes are unavoidable in disaster situations, it is possible for lifestyle-related
factors, especially satisfaction of sleep and participation in
recreation and community activity, to attenuate the association between changes in SES due to disaster and poor
subjective health. After a disaster, evacuees receive various
forms of support to help them rebuild their lives. We have
shown that improving satisfaction of sleep and participation in recreation and community activity through recovery support efforts may prevent the deterioration of the
subjective health.
Additional file
Additional file 1: Table S1. Prevalence ratios and 95% confidence
intervals of poor subjective health by change in living arrangements
among 14,913 men and 18,437 women aged 20–64 years in Fukushima
Health Management Survey, Fukushima, 2012. Table S2. Prevalence ratios
and 95% confidence intervals of poor subjective health by change in
working condition among 14,913 men and 18,437 women aged 20–
64 years in Fukushima Health Management Survey, Fukushima, 2012.
Table S3. Prevalence ratios and 95% confidence intervals of poor
subjective health by lifestyle-related factors among 14,913 men and
18,437 women aged 20–64 years in Fukushima Health Management
Survey, Fukushima, 2012. (DOCX 59 kb)
Abbreviations
CIs: Confidence intervals; PRs: Prevalence ratios; SD: Standard deviation;
SES: Socioeconomic status
Acknowledgements
Not applicable.
Funding
This survey was partly supported by the National Health Fund for Children
and Adults Affected by the Nuclear Incident.
Availability of data and materials
No additional data available.
Authors’ contributions
MN and TO contributed to the design of the study. TO, MM, SY, and MA
participated in the data collection. MN participated in the data analysis. MN
and TO participated in the manuscript writing. TO, WZ, HN, MM, SY, and MA
participated in the critical revision of the manuscript. All authors approved
the final version of the report for submission.
Page 8 of 9
Authors’ information
The findings and conclusions of this article are solely the responsibility of the
authors and do not represent the official views of Fukushima Prefecture
government.
Competing interests
The authors declare that they have no competing interests.
Consent for publication
Not applicable.
Ethics approval and consent to participate
The study protocol was approved by the Ethics Committee of Fukushima
Medical University. Participants who returned the self-administered questionnaires were considered to have consented to participate.
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
Author details
1
Radiation Medical Science Center for the Fukushima Health Management
Survey, Fukushima Medical University, Fukushima, Japan. 2Department of
Epidemiology, Fukushima Medical University School of Medicine, Fukushima,
Japan. 3Department of Disaster Psychiatry, Fukushima Medical University
School of Medicine, Fukushima, Japan. 4Department of Public Health,
Fukushima Medical University School of Medicine, Fukushima, Japan.
Received: 14 December 2015 Accepted: 8 April 2017
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